1. Field of Invention
The present invention relates to the detection of narrowband signals and, more specifically, to a system and method for detecting of a narrowband signal of known frequency in a wideband fluctuating noise.
2. Description of Prior Art
The detection of a narrowband signal amidst wideband noise is an important feature in communication devices ranging from cellular telephones to human hearing aids. To detect a target signal, systems typically use a filter tuned near the frequency of the target signal that rejects the remaining noise frequencies. The ability of such a system to detect a target signal is often affected by the signal-to-noise ratio (SNR), and the effectiveness of such a system is susceptible to fluctuations in the noise level that causes fluctuations in the output energy of the filter.
Other systems for detecting a narrowband signal use previously determined information about the noise to construct a filter that is matched to the properties of the noise, such as a Wiener filter. A system such as this depends on prior knowledge of the properties of the noise, however, and is ineffective when the noise varies or is indeterminate. Some systems, such as a Kalman filter, depend on a running estimate of the properties of the noise and use a time-varying filter to optimize the signal-to-noise (SNR) ratio. These systems, however, require sophisticated modeling of the noise and require complex algorithms.
Another large class of signal detectors correlate the incoming signal and noise with a template for the target signal. These detector systems require knowledge of the incoming signal characteristics and cannot always discern signals that do not have perfect tones or long-term temporal stationarity.
3. Objects and Advantages
It is a principal object and advantage of the present invention to provide a system and method for detecting a narrowband signal in wideband noise having fluctuating characteristics, such as amplitude.
It is an additional object and advantage of the present invention to provide a system and method for detecting a narrowband signal that does not require prior knowledge of the properties of the noise.
It is a further object and advantage of the present invention to provide a system and method for detecting a narrowband signal that is not a perfect tone or does not have long-term temporal stationarity.
It is another object and advantage of the present invention to provide a system and method for detecting a narrowband signal that does not require lengthy processes or sophisticated algorithms.
Other objects and advantages of the present invention will in part be obvious, and in part appear hereinafter.